In many sports, such as soccer, handball, or volleyball, it is desirable to provide additional information regarding various parameters of the sport to individuals watching the game. This concerns, for example, the position of the players and the ball at any time during the game, information concerning the velocity of the ball, and the speed and performance of individual players. Also, referees and other persons monitoring the game for compliance with the rules may benefit from such information and control the game more reliably. Additionally, it is also reasonable from a trainer's or an athlete's medical attendant's point of view not only to observe the events on the field, but also to obtain reliable data on the exact course of the game.
Therefore, several methods have been suggested in recent years wherein a transmitter is arranged in the ball and possibly further transmitters are arranged on the players, which emit or reflect electromagnetic waves or other signals. These signals can be captured by suitably arranged receivers and provide the desired information concerning the position and velocity of an object, for example the ball, at any arbitrary point in time during the game. Examples of such tracking systems are disclosed in German patent publication Nos. DE 42 33 341 C2, DE 100 55 289 A1, DE 100 29 464 A1, DE 100 29 456 A1, DE 100 29 463 A1, and DE 200 04 174 U1, the entire disclosures of which are hereby incorporated by reference herein.
An absolute necessity for the optimal operation of such a tracking system is a reliable and permanent arrangement of a transmitter or reflector within the ball. This is a considerable problem, in particular in the case of larger balls with an inflatable bladder, such as a soccer ball. Suspension of the transmitter should cushion all of the mechanical loads arising under deformations or accelerations of the ball to avoid damage to the electronic components. Moreover, the inserted transmitter should preferably not influence the mechanical properties and the trajectory of the ball. Further, many applications require an exact determination as to when the center of the ball has passed a certain line, for example the goal line of a soccer goal. Therefore, the transmitter should take an exactly defined position within the ball and maintain it permanently.
The approaches known from the prior art for the solution of this problem concern until now only constructions wherein the transmitter or a corresponding device is freely suspended by several elastic wires or similar devices within the bladder of the ball. Such arrangements are, for example, disclosed in the already mentioned DE 200 04 174 U1 and DE 100 29 459 A1, and in PCT application no. WO 97/20449 and French Patent No. 2 667 510, the entire disclosures of which are hereby incorporated by reference herein. Similar constructions are also disclosed in U.S. Pat. No. 6,251,035 B1 and German patent publication no. DE 829 109, the entire disclosures of which are hereby incorporated by reference herein. The last two documents concern objects that are positioned in the interior of the ball.
Presently known solutions, however, have several disadvantages: It is very difficult and requires a multitude of manual process steps to produce the bladders disclosed in the prior art and the corresponding balls; and the bladders known until now do not have the required stability to permanently protect the sensitive electronic components against damages. Moreover, to date, a reliable and permanent positioning of electronic components in the center of the ball could not be achieved.
Measures for increasing the stability of a bladder per se are disclosed in U.S. Pat. No. 4,826,177 and German Patent No. DE 39 18 038 C2, the entire disclosures of which are hereby incorporated by reference herein. These documents, however, concern only the shape stability of the ball (for example of a cubic ball or an exactly round ball with the common spherical shape, respectively) and do not provide any suggestions for improving the stability within the interior of the bladder or for a suitable suspension of a sensitive device.
There is, therefore, a need for a bladder for an inflatable ball, in particular a soccer ball, which is capable of maintaining a transmitter or other electronic device in a predetermined position and which sufficiently cushions arising loads to avoid damage to the device. There is a further need for such a bladder to be cost-efficient to manufacture and to not negatively affect the other properties of the ball.